MINERALOGY. 275 



er, would make it necessary to refer the species to different 

 systems from those now accepted. For example, leucite, re- 

 ferred to above, he would make monoclinic; boracite is made 

 orthorhombic ; also garnet, fluorite, senarmontite, and anal- 

 cite are considered only pseudo-isometric; and an analogous 

 change is argued in the case of apophyllite, vesuvianite, ru- 

 tile, zircon, apatite, beryl, tourmaline, topaz, and other well- 

 known species. 



Another writer, G. Grattarola, in Florence, supplements the 

 list of Mallard with a number of species which, on grounds 

 which seem by no means sufficient, he would refer to other 

 systems lower in regard to symmetry of form; for example, 

 calcite, barite, nephelite, and so on. He argues that in fact 

 we can regard only one system as having a real existence ; 

 that is the most complex and least symmetrical system, the 

 triclinic system. Moreover, as an author remarks in review- 

 ing the subject, even this system he seems to think too reg- 

 ular to be thoroughly satisfactory. 



Aside from these partially theoretical results reached by 

 the writers referred to, which seem to threaten to overthrow 

 the rigid dividing-lines between the different systems, and 

 to reduce crystallography to a far less simple subject than 

 it is at present, there are a number of cases in which the 

 change of system cannot be questioned. Thus Tschermak 

 has shown most conclusively that all the micas are mono- 

 clinic. Moreover, his observations have made it extremely 

 probable that corundum is also monoclinic instead of rhom- 

 bohedral. Again, the peculiar form of silica, described by 

 Vom Rath as hexagonal, under the name of tridymite, is now 

 shown to be in fact triclinic, the apparently hexagonal form 

 being due only to twinning. The same conclusion must be 

 accepted in regard to milerite, which is now made ortho- 

 rhombic instead of hexagonal. Harmotome was transferred 

 to the monoclinic system by Des Cloizeaux, and now La- 

 saulx argues that the same change must be made for stilbite. 

 Perofskite, which was once made isometric, and whose system 

 has long been in doubt, is now made orthorhombic by Kok- 

 scharof. The above list might be easily increased. 



Of recent crystallographic memoirs remarkable for their 

 complete and comprehensive character, several deserve es- 

 pecial mention. One of these is devoted to epidote by Buck- 



